In the prior art, a geared transmission capable of changing a gear stage thereof stepwise, and a continuously variable transmission capable of varying a speed change ratio steplessly are available as a transmission mechanism for transmitting power between rotary members. For example, a belt-type continuously variable transmission and a toroidal-type continuously variable transmission are known as the continuously variable transmission. Specifically, the belt-type continuously variable transmission is a transmission varying a speed change ratio continuously using a pair of drive pulleys and a pair of driven pulleys, and a driving belt applied to those pulleys. The known endless driving belt used in such belt-type continuously variable transmission is prepared by arranging a plurality of plate members called an “element” or a “block” in a circular manner while connecting the plate members with one another, and fastening the interlinked plate members by an annular belt called a “band” or a “carrier”.
When the driving belt of this kind applied to the drive and driven pulleys is driven by driving the drive pulley, a frictional force acts on a contact portion between the element and the drive pulley, and a compressive force is applied to the elements in the arranging direction thereof, i.e., in the thickness direction thereof according to a torque of the drive pulley. The compressive force applied to the element being contacted with the drive pulley is transmitted to the element being contacted with the driven pulley via the elements existing between the drive and driven pulleys. When the compressive force is transmitted to the element being contacted with the driven pulley, a frictional force is generated at the contact portion between the element and the driven pulley, and a torque to rotate the driven pulley is established according to the transmitted compressive force. The power is thus transmitted between the drive and driven pulley through the driving belt.
One example of above-explained driving belt is disclosed in Japanese Patent Laid-Open No. 2000-249195. The “High-Loaded Transmission Belt” taught by Japanese Patent Laid-Open No. 2000-249195 is composed of a center belt and blocks reinforced against lateral pressure, and it is applied to a main prime mover and an auxiliary prime mover of automobiles and agricultural machineries. Specifically, the “High-Loaded Transmission Belt” comprises a block (i.e., an element) which is so constituted that two belt sides having lock parts in its top end are connected to each other in their bottom ends by a connecting member, and two rows of endless carriers (i.e., rings) fixedly fitted into an engagement groove opening between the lock parts. The belt side portion of the element is provided individually with a convex portion and a concave portion on each face so that the elements can interlink with one another. Therefore, the interlinked elements can be aligned even when the belt is running.
In addition to above, Japanese Patent Laid-Open No. 2001-193796 discloses an invention relating to “Element for Metal Belt and Metal Belt” for continuously variable transmissions of vehicles. The metal belt taught by Japanese Patent Laid-Open No. 2001-193796 comprises: a metal endless band (i.e., a ring) applied to annular grooves of a drive and a driven pulleys; a plurality of metal element composed of a body portion to be contacted with the annular groove of the pulley, a pair of pillars erected on the body portion and faced with each other, an engagement protruded portion formed on a leading end of the pillar, and an opening for inserting the band (i.e., a recessed portion) formed between the engagement protruded portions; and an endless metal falling preventing body somewhat wider than the band. The falling preventing body can be bent to narrow its width when it is inserted in between the engagement protruded portions to prevent falling of the band.
The transmission belt taught by Japanese Patent Laid-Open No. 2000-249195 comprises lock parts on both of the belt sides of the block to hold the two rows of carriers in the block. According to the transmission belt taught by Japanese Patent Laid-Open No. 2000-249195, the two rows of carriers have to be overlapped partially when fitting the carriers into the block or detaching the carriers from the block. Specifically, the total width of the carriers has to be reduced narrower than the opening width between the lock parts by twisting the rings to overlap portions of the carriers in its length direction when fitting the carriers into the block or detaching the carriers from the block.
That is, the two rows of carriers can be fitted into the block from the overlapped portion through between the lock parts by partially overlapping the carriers aligned parallel to each other to reduce the total width thereof narrower than the clearance between the lock parts. For example, as shown in accompanying FIG. 8, two rows of rings R1 and R2 are fitted into the recess of the element E from the overlapped portion (shown in the circle “a” in FIG. 8), and the element E holding the rings R1 and R2 is moved in the length direction of the rings R1 and R2 to the portion (shown in the circle “b” in FIG. 8) where the rings R1 and R2 are aligned parallel to each other. As a result, the rings R1 and R2 are situated in an inner circumferential side of the latch portions (in the assembled driving belt) to be fitted in the recess of the element E properly.
In order to overlap the rings aligned parallel to each other partially in its length direction while keeping remaining portion of the rings parallel to each other, the remaining portions of the rings have to be held parallel to each other when overlapping the rings partially.
However, if one of the rings aligned parallel to each other is situated inside of the other ring to be overlapped partially, the remaining portions of the rings move apart from each other and this makes difficult to handle the rings. For example, the inner ring R1 may cross the outer ring R2 as shown in FIG. 9. This makes difficult to fit the rings into the recess of the element. Moreover, the elements holding the rings may be detached from the rings.
Thus, the conventional arts thus far explained are incapable of holding the plurality of rings parallel to each other stably while overlapping the rings partially in its length direction. Therefore, the driving belt cannot be assembled easily by the conventional arts.